WASHINGTON (AP) — The drilling procedure called fracking didn’t cause much-publicized cases of tainted groundwater in areas of Pennsylvania and Texas, a new study finds. Instead, it blames the contamination on problems in pipes and seals in natural gas wells…

Cornell University engineering professor Anthony Ingraffea, who wasn’t part of the study, praised it, adding that he’s worried because “it’s impossible to drill and cement a well that will never leak.”

“There’s still serious and significant harm from what’s coming before fracking and what’s coming after fracking,” Ingraffea said.

After California state regulators shut down 11 fracking wastewater injection wells last July over concerns that the wastewater might have contaminated aquifers used for drinking water and farm irrigation, the EPA ordered a report within 60 days.

It was revealed yesterday that the California State Water Resources Board has sent a letter to the EPA confirming that at least nine of those sites were in fact dumping wastewater contaminated with fracking fluids and other pollutants into aquifers protected by state law and the federal Safe Drinking Water Act.

The letter, a copy of which was obtained by the Center for Biological Diversity, reveals that nearly 3 billion gallons of wastewater were illegally injected into central California aquifers and that half of the water samples collected at the 8 water supply wells tested near the injection sites have high levels of dangerous chemicals such as arsenic, a known carcinogen that can also weaken the human immune system, and thallium, a toxin used in rat poison.